I saw a lot of programmers who have no prior exposure to frontend are stuggling with React especially with the functional part(etc. hooks).They are more familiar with backend programming languages like Python, Java, C++, etc. So I decided to write a guide to help them understand React better.

How to get started with React

React mostly uses a syntax extension of JavaScript called JSX. JSX is a syntax that allows you to write HTML elements in JavaScript and place them in the DOM without any createElement() and appendChild() methods. It’ll be easier to understand if you have some experience with HTML and JavaScript. If you don’t have prior experience with HTML, you can learn it from W3Schools or MDN Web Docs.

Here is an example of JSX:

const element = <h1>Hello, world!</h1>

You can put any valid JavaScript expression inside the curly braces in JSX. For example:

const name = "Josh Perez"
const element = <h1>Hello, {name}</h1>

You can also use JSX inside of JavaScript functions: Here we use a variable called user to display a greeting message, it could be a string or null.

function getGreeting(user) {
  return user ? <h1>Hello, {user}!</h1> : <h1>Hello, Stranger.</h1>
}

or you can use javascript expressions inside of JSX:

const getGreeting = user => {
  return <h1>Hello, {user ? user : "Stranger"}!</h1>
}

React Components

React components are small, reusable pieces of code that return a React element to be rendered to the page. The simplest version of a React component is a plain JavaScript function that returns a React element.

Here is an example of a React class component:

class Welcome extends React.Component {
  render() {
    return <h1>Hello, {this.props.name}</h1>
  }
}

And here is an example of a React functional component:

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>
}

In short, React components are like JavaScript functions. They accept arbitrary inputs (called “props”) and return React elements describing what should appear on the screen.

React Hooks

React hooks are functions that let you use state and other React features in functional components. They are introduced in React 16.8.

Here is an example of a React functional component with hooks:

import React, { useState } from "react"

function Example() {
  // Declare a new state variable, which we'll call "count"
  const [count, setCount] = useState(0)

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  )
}